This invention relates to a pneumatic rotation grinder which comprises a housing with a pressure air inlet passage and a manually operable throttle valve, a rotation motor drivingly connected to an output shaft on which a grinding tool is attachable, a safety guard adjustably supported on the housing in a coaxial disposition relative to the output shaft, and a lock means located between the safety guard and the housing and arranged to arrest the safety guard in desired angular positions relative to the housing.
A prior art rotation grinder of the above type is described in E.P. 0 322 626 (corresponding to U.S. Pat. No. 4,924,634). This previously known tool comprises a safety guard that is rotationally locked to the tool housing by means of a latch element in selective cooperation with a number of teeth or holes on the safety guard.
A drawback inherent in this known concept is that the inevitable play, although small, existing between the safety guard and the housing as well as between the latch element and the teeth or holes in the safety guard will cause a rattling of the latter during operation of the tool. This rattling will in turn result not only in an annoying noise but after some time also in a deformation of the latch element and the cooperating teeth or holes, which will increase the rattling, and so on. This problem will be significant if the safety guard is of the vibration damping type having additional weights supported thereon.
The above problem is solved by the invention.
A preferred embodiment of the invention is described below in detail with reference to the accompanying drawings.